To develop suitable prevention and response strategies, it is essential
to identify the sources of oil discharge into the marine environment, as
well as their contribution to the phenomenon of “black
tides”. This is no easy task. Although accidents involving oil
spills may be well documented, the same cannot be said for the rest.
For example, incidences of operational
discharge can only be assessed approximately.

Accidental discharge

In the same way, the reliability of data on industrial and urban discharge
is highly variable from one country to another. The extent of discharge
from natural sources can only be estimated in a very general fashion. It
is therefore not surprising to see considerable variation in the quantities
quoted from one document to another.

The diagram below presents the data used as a reference in the work of the
International Maritime Organization.

Only direct discharges into the water have been included here, excluding
the share of atmospheric emissions that rain and streams transfer into the
water. The method used to estimate such sources varies from one documentary
source to another, generating estimations that are not always consistent.

The accidental release of oil, or other petroleum products usually into
freshwater or marine ecosystems, and usually in large quantities. It can
be controlled by chemical dispersion, combustion, mechanical containment,
and absorption. (Source: EEA multilingual environmental glossary, http://glossary.eea.europa.eu/EEAGlossary,
October 2006)

A form of pollution in which oil from various sources leaks into the water.
(Source: US Environmental Protection Agency)[Click here to see disclaimer]

Black tide: definitions

A major oil slick which threatens to reach and pollute the shore (Source:
ZILBERBERG. Elsevier’s Dictionary of Marine Pollution)[Click here to see copyright]